The present invention relates to a sheet stacking apparatus which stacks, on a pallet, sheets conveyed from a printing unit, coating unit, or the like, and extracts a predetermined number of stacked sheets from the apparatus.
A sheet stacking apparatus of this type includes sensors for detecting that the operator has entered, during an operation, an extraction portion to be used to extract sheets from the apparatus. If the operator has entered from the extraction portion into the apparatus during the operation, the sensors detect it to stop the operation of the apparatus (printing press). This allows to prevent the operator from erroneously entering the apparatus during the operation. On the other hand, to extract a predetermined number of stacked sheets from the apparatus via the extraction portion, the operator operates a manual button to disable the detection operation of the sensors.
The conventional sheet stacking apparatus has three extraction portions for various kinds of operations including extraction of a predetermined number of stacked paper sheets from a sheet stacking unit that stacks paper sheets conveyed from a printing press. Each extraction portion has a safety device for the delivery apparatus, which includes first to third detection sensors for detecting entering of the operator or the like, and a detection cancel device for disabling the detection operation of the detection sensors (patent reference 1).    [Patent reference 1] WO 2004/078626A1
The above-described detection cancel device includes a detection cancel key A configured to cancel a first detection sensor of the upper part for sampling or pile adjustment, a detection cancel key B configured to cancel a third detection sensor of the lower part when making the fork of a forklift enter the stacking unit, and a detection cancel key C configured to cancel the first to third detection sensors of the upper, middle, and lower parts when delivering stacked sheets from the stacking unit.
In the conventional sheet stacking apparatus having the above-described arrangement, to deliver stacked sheets from the stacking unit, the detection cancel key B is operated first to make the fork enter the stacking unit. After that, the detection cancel key C is operated to make the fork exit. That is, since not only the detection cancel key B but also the detection cancel key C needs to be operated, the operator finds operating the detection cancel key C cumbersome and may forget it.